<?php

if (! defined('BASEPATH'))
    exit('No direct script access allowed');

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package CodeIgniter
 * @author ExpressionEngine Dev Team
 * @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license http://codeigniter.com/user_guide/license.html
 * @link http://codeigniter.com
 * @since Version 1.0
 * @filesource
 *
 */
    
// ------------------------------------------------------------------------

/**
 * Database Cache Class
 *
 * @category Database
 * @author ExpressionEngine Dev Team
 * @link http://codeigniter.com/user_guide/database/
 */
class CI_DB_Cache
{

    var $CI;

    var $db;
 // allows passing of db object so that multiple database
             // connections and returned db objects can be supported
    
    /**
     * Constructor
     *
     * Grabs the CI super object instance so we can access it.
     */
    function __construct (&$db)
    {
        // Assign the main CI object to $this->CI
        // and load the file helper since we use it a lot
        $this->CI = & get_instance();
        $this->db = & $db;
        $this->CI->load->helper('file');
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Set Cache Directory Path
     *
     * @access public
     * @param
     *            string the path to the cache directory
     * @return bool
     */
    function check_path ($path = '')
    {
        if ($path == '') {
            if ($this->db->cachedir == '') {
                return $this->db->cache_off();
            }
            
            $path = $this->db->cachedir;
        }
        
        // Add a trailing slash to the path if needed
        $path = preg_replace("/(.+?)\/*$/", "\\1/", $path);
        
        if (! is_dir($path) or ! is_really_writable($path)) {
            // If the path is wrong we'll turn off caching
            return $this->db->cache_off();
        }
        
        $this->db->cachedir = $path;
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Retrieve a cached query
     *
     * The URI being requested will become the name of the cache sub-folder.
     * An MD5 hash of the SQL statement will become the cache file name
     *
     * @access public
     * @return string
     */
    function read ($sql)
    {
        if (! $this->check_path()) {
            return $this->db->cache_off();
        }
        
        $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(
                1);
        
        $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(
                2);
        
        $filepath = $this->db->cachedir . $segment_one . '+' . $segment_two . '/' .
                 md5($sql);
        
        if (FALSE === ($cachedata = read_file($filepath))) {
            return FALSE;
        }
        
        return unserialize($cachedata);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Write a query to a cache file
     *
     * @access public
     * @return bool
     */
    function write ($sql, $object)
    {
        if (! $this->check_path()) {
            return $this->db->cache_off();
        }
        
        $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(
                1);
        
        $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(
                2);
        
        $dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
        
        $filename = md5($sql);
        
        if (! @is_dir($dir_path)) {
            if (! @mkdir($dir_path, DIR_WRITE_MODE)) {
                return FALSE;
            }
            
            @chmod($dir_path, DIR_WRITE_MODE);
        }
        
        if (write_file($dir_path . $filename, serialize($object)) === FALSE) {
            return FALSE;
        }
        
        @chmod($dir_path . $filename, FILE_WRITE_MODE);
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Delete cache files within a particular directory
     *
     * @access public
     * @return bool
     */
    function delete ($segment_one = '', $segment_two = '')
    {
        if ($segment_one == '') {
            $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(
                    1);
        }
        
        if ($segment_two == '') {
            $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(
                    2);
        }
        
        $dir_path = $this->db->cachedir . $segment_one . '+' . $segment_two . '/';
        
        delete_files($dir_path, TRUE);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Delete all existing cache files
     *
     * @access public
     * @return bool
     */
    function delete_all ()
    {
        delete_files($this->db->cachedir, TRUE);
    }
}


/* End of file DB_cache.php */
/* Location: ./system/database/DB_cache.php */